How to use the desert.color.white function in desert

  def init(self, fg=black(0.01), bg=white()):
    self.fg = fg
    self.bg = bg
    self.clear()
    return self

def main(arg):

  with Desert(1000, show=True, verbose=VERBOSE)\
      .init(fg=black(0.001),
            bg=white()) as c:

    density = 0.02
    a = random(2)*TWOPI
    acc = zeros(2)
    noise = 0.000000005
    rad = 0.45

    resa = []
    resb = []

    for i in range(4000000):
      a += acc
      acc += (1-2*random(2))*noise

      resa.append((cos(a[0]), sin(a[0])))
      resb.append((cos(a[1]), sin(a[1])))

def main(arg):

  with Desert(1000, show=True, verbose=VERBOSE)\
      .init(fg=black(0.001),
            bg=white()) as c:

    density = 0.15
    num = 20
    rad = 0.35

    noise = 0.00005
    spl = []

    for _ in range(20):
      a = sorted(random(num)*TWOPI)
      spl.append(0.5 + column_stack((cos(a), sin(a)))*rad)

    res = []
    for i in range(1, 4000000):
      for xy in spl:
        n = xy.shape[0]

def main(arg):

  imsize = 1000
  with Desert(imsize, verbose=VERBOSE)\
      .init(fg=black(0.1),
            bg=white()) as desert:

    num = 20

    xya = random((num, 2))
    xyb = random((num, 2))

    stacka = []
    stackb = []

    drift = in_circle(1, 0, 0, 0.00001)

    for i in range(1, 100000):
      xya += in_circle(num, 0, 0, 0.001) + drift
      xyb += in_circle(num, 0, 0, 0.001) + drift
      stacka.append(xya.copy())
      stackb.append(xyb.copy())

def main(arg):

  imsize = 1000
  with Desert(imsize, verbose=VERBOSE)\
      .init(fg=rgb(1.0, 0.0, 0.0, 0.1),
            bg=white()) as desert:

    draw = desert.draw

    draw([box(0.15, (0.3, 0.3), 2.0),
          box(0.2, (0.2, 0.5), 0.1),
          box((0.05, 0.5), (0.25, 0.9), 1.0),
          box((0.3, 0.2), (0.1, 0.9), 2.0)])

    desert.show()

    desert.set_fg(rgb(0, 0.5, 0.5, 0.1))

    draw([box(0.15, (0.5, 0.3), 2.0),
          box(0.2, (0.5, 0.5), 0.1),
          box((0.05, 0.5), (0.6, 0.9), 1.0),
          box((0.1, 0.2), (0.3, 0.9), 1.0)])

def main():

  with Erosion(verbose=VERBOSE)\
      .init(fg=rgb(1.0, 0.0, 0.0, 0.1),
            bg=white()) as erosion:

    send = erosion.send

    send([box(0.15, (0.3, 0.3), 2.0),
          box(0.2, (0.2, 0.5), 0.1),
          box((0.05, 0.5), (0.25, 0.9), 1.0),
          box((0.3, 0.2), (0.1, 0.9), 2.0)])

    erosion.set_fg(rgb(0, 0.5, 0.5, 0.1))

    send([box(0.15, (0.5, 0.3), 2.0),
          box(0.2, (0.5, 0.5), 0.1),
          box((0.05, 0.5), (0.6, 0.9), 1.0),
          box((0.1, 0.2), (0.3, 0.9), 1.0)])

    erosion.set_fg(rgb(0, 0.0, 0.8, 0.1))